The present invention relates to substituted tetrahydroimidazopyridine compounds, processes for the preparation thereof, pharmaceutical compositions containing these compounds, and the use of these compounds for the preparation of medicinal products and the treatment or inhibition of pain and other conditions.
The treatment of pain, in particular neuropathic pain, is of great importance in medicine. There is a worldwide need for effective pain therapies. The urgent need for action to find targeted, patient-appropriate treatment for chronic and non-chronic pain conditions, this being understood as the successful and satisfactory treatment of pain for the patient, is also documented in the large number of scientific works that have been published in recent times in the field of applied analgesics and basic research into nociception.
A pathophysiological feature of chronic pain is the overexcitability of neurons. Neuronal excitability is decisively influenced by the activity of K+ channels, since these significantly determine the resting potential of the cell and hence the excitability threshold. Heteromeric K+ channels of the molecular subtype KCNQ2/3 (Kv7.2/7.3) are expressed in neurons of various regions of the central (hippocampus, amygdala) and peripheral (dorsal root ganglia) nervous system and regulate the excitability thereof. Activation of KCNQ2/3 K+ channels leads to a hyperpolarisation of the cell membrane and, accompanying this, to a decrease in the electrical excitability of these neurons. KCNQ2/3-expressing neurons of the dorsal root ganglia are involved in the transmission of nociceptive stimuli from the periphery into the spinal cord (Passmore et al., J. Neurosci. 2003; 23(18):7227-36). It has accordingly been possible to detect an analgesic activity in preclinical neuropathic and inflammatory pain models for the KCNQ2/3 agonist retigabine (Blackburn-Munro and Jensen, Eur J. Pharmacol. 2003; 460(2-3):109-16; post et al., Naunyn Schmiedeberg's Arch Pharmacol 2004; 369(4): 382-390). The KCNQ2/3 K+ channel thus represents a suitable starting point for the treatment of pain; in particular pain chosen from the group consisting of chronic pain, neuropathic pain, inflammatory pain and muscular pain (Nielsen et al., Eur J. Pharmacol. 2004; 487(1-3): 93-103), in particular neuropathic and inflammatory pain.
Moreover, the KCNQ2/3 K+ channel is a suitable target for therapy of a large number of further diseases, such as, for example, migraine (US2002/0128277), cognitive diseases (Gribkoff, Expert Opin Ther Targets 2003; 7(6): 737-748), anxiety states (Korsgaard et al., J Pharmacol Exp Ther. 2005, 14(1): 282-92), epilepsy (Wickenden et al., Expert Opin Ther Pat 2004; 14(4): 457-469) and urinary incontinence (Streng et al., J Urol 2004; 172: 2054-2058).